DISEÑO Hurst embodiment

8/2/2019 DISEO Hurst embodiment

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MTODOS DE DISEO

EMBODIMENT

(Anlisis)

Engineering Design Principles, KenHurst, 1999, Elsevier.


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Concept developmentEMBODIMENT

A more detailed analysis of the selectedconcept(s) is undertaken.

The output is a definitive scheme drawingaccompanied by documentation, such as

calculations, required tolerances andsuggested materials and manufacturingprocesses,which explains the design intent.


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EMBODIMENT

Although a 3D representation is very usefulduring the embodiment stage it is of no useduring the detail stage and scheme drawings,

drawn strictly to scale, are essential.


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EMBODIMENT

Concept C, was theselected concept forthe seat suspension

exercise


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EMBODIMENT

Fig. 5.1 highlights many embodiment issues. The more obviousinclude:

How is the suspension travel to be provided?

What is the required size and strength of structural components?

Can a damper of the required proportions be purchased?

Are adjustment handles ergonomically acceptable?

Will welded joints be acceptable?

What are the implications for manufacture and assembly?


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EMBODIMENT

The final design will involve compromisebetween conflicting requirements.

Many actions must be performed at the sametime and the solution synthesized

Decisions made in one area can have a knockon effect elsewhere.


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EMBODIMENT The embodiment

is cyclical oriterativefollowing broadly

the pattern inthe outer ring ofthe figure.

It begins with adecision beingmade on overall

layout.


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EMBODIMENT

This is then modelled, analysed, synthesizedand optimized.

A revised layout is then produced or moredetail added to the original.

The embodied design is evaluated against thefunctions and constraints in the PDS.


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EMBODIMENT

Process is repeated many times and fordifferent areas of a design, until the bestcompromise solution, taking into accountmanufacturing and assembly processes andmaterials selection, is reached.


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EMBODIMENT

The value engineering process runs in parallel

Value engineering establishes the cost and

performance of alternative proposals

Synthesis of all the information including cost

estimates, guides the team in thedevelopment of an optimum design proposal.


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EMBODIMENT

The following sections outline the process.

Size and strength

Scheme drawing

Form design

Provisional materials and process

determination

Design for assembly and manufacture

Industrial design


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EmbodimentSize and strength

Identify those functions and constraints withinthe PDS which will influence and determineoverall size and strength.

Those factors include operator weight andsize, maximum frequencies of vibration,

required factors of safety, etc.

b


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EmbodimentScheme drawing

All known parameters included.

Include all motion, to ensure adequate clearances,and copious notes indicating decisions made onsubjects such as tolerances and materials.

Regularly updated and modified as the embodimentprocess continues.


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Scheme drawing

Important method of controlling the knock oneffects and implications of decisions.

It is drawn to scale: only very important dimensions,usually those which include tight tolerances, areincluded.

Standard and bought out parts can influencedecisions greatly since sizes and availability arenormally set and restricted respectively.


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Scheme drawing

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EmbodimentForm design

This process can be further divided byconsidering the primary function first andthen repeating the cycle for each secondary

function.

It is important that, during this phase, some

provisional thought centres on the likelymanufacturing and assembly processes.


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Form design

Decisions made at the embodiment design stagedictate manufacturing processes

It is imperative that manufacturing engineers, if notpart of the design team, are at least consultedbefore decisions are made.


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Form design

There are obviously advantages and disadvantagesto each manufacturing process , often the decisionis made on cost against quantity grounds.

Ejemplo:

Consider the design of a link which must have acentral pivot and two guide holes at its extremities.The likely manufacturing processes to beconsidered are casting, drop forging, hammerforging and welding.


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Form design


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Form design

The cross-section and overall shape would be

influenced by each process.

Cast iron is not as strong in tension and bending as

steel so more material is required and the cross-section must be much thicker.

Drop forged steel will use the least material of all.

Manufacturing process to choose is always

influenced by the quantities to be manufactured.


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Form design


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Form design

Load paths have a great influence on the shape andform of components.

The ideal is that components are subjected to puretension and compression.

One of the prime requirements in the design of theblock is to ensure smooth transition of load.


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Form design


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Form design

In the suggested design in (c) the webs are incompression only and the stresses caused by theload are smoothly transferred through the bearingblock.


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Form design

Ejemplo:

Component for translating reciprocating horizontalmotion into reciprocating vertical motion is the bell-

crank lever.

In (a), this design has to be relatively thick to prevent

deflection due to bending. (b), which at first sightlooks wrong because we do not commonly seedesigns like it, can involve 50% less materialbecause bending is almost completely designed out.


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Form design


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Form design

The effect of size can be illustrated, by consideringagain the bearing block.

The larger the height dimension becomes thelighter or thinner the form should become.

The centre section of the larger block is thus hollow.


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Form design

E b di


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EmbodimentProvisional materials and process

determination There are well over 15 000 engineering materials

to choose from.

Materials account for approximately 50% of thecost of an average manufactured product.

A further complication in the selection ofmaterials and processes is the possibility ofimproving component characteristics by surface

coating the component.


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Form design

The proper use of materials leads to increased

product performance, greater efficiency andreduced costs, resulting in increasedcompetitiveness for companies.

At the limits of science and technology, materialsare being developed for specific tasks. These arespecialized materials with little general applicability.In such circumstances the material the designermust employ (and the associated process) in thesolution would form one of the constraints in the

specification.


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Form design

If the specification is thorough and complete, the

selection of material and process should be clearlyconstrained. From the specification, the maincriteria may be identified and can often be a ratio

such as cost/unit volume, cost/weight orstrength/weight.

Indeed, quantitative methods of selection are oftenbased on ratios such as these.


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Form design

The decision making process is best carried out as

an elimination process. Start by excluding thosematerials and processes which clearly are notsuitable.


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Form design

The main criteria used to select the combination of

materials and processes are:

availability cost quantity required tolerancesrequired vibration damping environmentalimpact density wear resistance surfaceroughness speed of delivery ease of machining

corrosion resistance styling possibilities operating environment friction coefficients chemical resistance electrical properties

mechanical properties.


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EmbodimentDesign for assembly and manufacture

Good practice dictates that during all stages ofthe design process advice is sought frommanufacturing experts

The designer should attempt to utilize existingmachinery and tooling where possible.


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Assuming that possible interference of components or

gross errors in the 'logic' of assembly are detectedduring the execution of the scheme drawing, adesign should be suitable for machining andassembly if the following are critically appraised:

ease of machining

economy

use of existing machinery and tooling

avoidance of redundant fits

accessibility

ease of assembly.


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Next figure illustrates provision of runouts for

cutting tools.

A poor finish may result or a component may beimpossible to manufacture without runouts.

The decision to provide such undercuts must betaken at the design stage since the smaller diametermay have strength reduction implications.


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f f


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Simplification of machining: placing of features in

the components which are easiest to machine andsubsequently inspect.

This is true of the grooves which are required forsome sort of rubber sealing ring

f bl d f


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i f bl d f


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To facilitate drilling, clearance must be provided for

the drill to break through fully.

Drills should encounter equal resistance on theircutting edges so should not enter on a slopingsurface

The centre of holes should be at least a fulldiameter away from the edge of a component toavoid breaking out.

D i f bl d f


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The final decision between manufacturing methods

is often based upon careful cost estimates of thealternatives.

As a general guide choose simple shapes, such ascylindrical or flat surfaces.

Try to avoid tapers and complex curves.

Use the most economical machining process:Turning is much more economical than grinding.

D i f bl d f


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Keep machining to a minimum by machining the

feet only.

Only machine working surfaces.

D i f bl d f


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Re-clamping or setting of tools during machining is

avoided by designing machined features at the sameheight.

Secure clamping is essential for accurate machining:ensure that faces, bosses and lugs are provided.

D i f bl d f t


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Provide lugs in the

blueprint that can beused to assist inholding or orientation

of the casting formachining.

Good designers are amachinist's best friend

www.jjjtrain.com

D i f bl d f t
http://www.jjjtrain.com/vms/eng_castings/eng_castings_07.htmlhttp://www.jjjtrain.com/vms/eng_castings/eng_castings_07.html


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Design for assembly and manufacture Avoid redundant fits: they demand excessively tight

tolerances.

In the next figure, the bush which is inserted in the hole in thehousing must have its depth of insertion controlled.

This can be accomplished by the single flange contactingthe face of the housing.

D i f bl d f t


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Optimize the number of components.

The smaller the number of components the easierassembly will be.

However, reducing the number of componentsimplies an increase in manufacturing complexity forthose components. This is trade off, but the initialaim should be to ascertain the minimum number ofcomponents.

D i f bl d f t


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If the answer to the following questions is no it is

possible that components could be combined:

Do the components move with respect to each

other?

Do the components have to be of different

materials?

Are separate components required for assembly and

disassembly?

D i f bl d f t


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The aim must be to make assembly easier rather

than just possible.

Symmetry is not desirable: the introduction offeatures which break symmetry helps to ensurecorrect assembly.

Assembly is greatly assisted by the addition of suchfeatures as lead-in chamfers.


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EmbodimentIndustrial design

It is very easy for engineering designers tobelieve that design is concerned only with

achieving a technically optimum solutionwhich will automatically satisfy aesthetic andergonomic aspects.

If competitive advantage is to be gained thewhole nature of the product must beaddressed.

Industrial design


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Industrial design

There are broadly three areas covering the

complete range of design activity: technical,ergonomic and aesthetic.

The basic aims of industrial design are:

Products must satisfy people in the ergonomic

sense.

Products should satisfy the natural human need

for beauty, style and status.


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Industrial design

Ergonomics

In the USA human engineering finds favourand in continental Europe the expressionbiotechnics is often used.

Ergonomics


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Ergonomics Some of the questions which should be addressed

during the design of products and processes whichinvolve human interaction:

What role is the operator expected to play? Will optimum use be made of inherent

human capacities?

How will the equipment fit the operator? Will the operator sit or stand?

Will the operator's posture be satisfactory?

Ergonomics


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Ergonomics

Is the section of population likely to

operate the equipment clearly defined? What information does the operator need

to perform the task? Should this information be visual, auditory

or tactile?

What type of display will give quickinformation with minimum ambiguity?

Ergonomics


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Ergonomics

What type of controls will be optimum?

How much force can the operator bereasonably expected to apply?

What form of communication isappropriate between operators?

What physical and mental work will the

operator be required to do? What are the ambient conditions likely to

be?


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Industrial design

Aesthetics

Confusion of visual form and the attributesattached can be caused by irrationality.

In interpreting the well-known next diagramsour eye and brain distort the images.

Aesthetics


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Aesthetics

A th ti


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Aesthetics

(a) the two vertical lines do not look the samelength

(b) the horizontal lines do not look straight

(c) we often miss the repeated word

(d) the horizontal lines do not look the samelength.

A th ti


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Aesthetics

When attention is either directed or attractedby any visual feature all other features tend tolose significance.

Embodiment


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EmbodimentPrinciples

Optimization The search is for the bestcompromise between conflicting criteria.

Simplification Load transmission and form should

be simplified. Scaling Full-scale models are rarely possible and

reduced size testing must be carried out carefully.


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Principles

Aesthetics The designer should aim for a visuallyappealing product.

Ergonomics A user friendly design is sought which

makes appropriate use of the inherent skills ofoperators.

Synthesis A solution is often arrived at by a

combination of techniques and elements. Iteration Progress towards the detail design stage

is made iteratively as knowledge ofthe importantfactors grows

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